Unit 7: Natural Selection and Continuing Evolution

Comprehensive vocabulary flashcards covering the concepts, mechanisms, cellular variations, and empirical evidence of natural selection and ongoing evolution.

Evolution

A change in the genetic makeup of a population over time, driven primarily by natural selection.

Natural Selection

A major, non-random mechanism of evolution where environmental conditions select for individuals with favorable phenotypes, allowing them to survive, reproduce, and pass those traits to subsequent generations.

Differential Survival

The unequal survival rate among individuals within a population caused by competition for limited resources.

Evolutionary Fitness

The measure of biological success evaluated specifically by an organism's reproductive success—its ability to survive and produce viable offspring.

Reproductive Advantage

The increased likelihood of surviving and reproducing possessed by individuals that are a better fit for their particular environment.

Artificial Selection

A non-random evolutionary mechanism in which humans selectively breed organisms for specific desirable phenotypes or traits.

Sexual Selection (Non-Random Mating)

A non-random evolutionary mechanism wherein individuals choose mating partners based on specific phenotypic traits.

Genetic Drift

A random evolutionary mechanism that causes non-adaptive fluctuations in allele frequencies from generation to generation, most prominently via the founder effect or bottleneck effect.

Founder Effect

A random form of genetic drift that occurs when a new, small population is established by a small number of individuals originating from a larger population.

Bottleneck Effect

A random form of genetic drift resulting from a drastic reduction in population size caused by a natural disaster, catastrophic event, or human-induced activity.

Gene Flow (Migration)

A random evolutionary mechanism involving the movement of individuals and their genetic material into or out of populations, which can lead to a loss of genetic variety in small populations.

Mutations

Random errors in genetic sequences that increase genetic diversity and serve as the original source of all genetic variation in populations.

Phenotypic Variation

The physical and physiological differences observable among individuals in a population upon which natural selection acts.

Selective Pressure

Biotic or abiotic environmental forces that affect the reproductive success and fitness of organisms within a population.

Biotic and Abiotic Environments

The living (biotic) and nonliving (abiotic) components of an ecosystem that can fluctuate or remain stable, determining the direction and rate of natural selection across generations.

Chlorophyll Diversity

The cellular presence of multiple photosynthetic pigment types (such as chlorophyll a and chlorophyll b) absorbing different light wavelengths to maximize energy capture throughout the day or across canopy layers.

Hemoglobin Variants

Stage-specific oxygen-transport proteins in humans, such as fetal hemoglobin ($\text{HbF}$, $\alpha_2\gamma_2$), which possesses a higher oxygen affinity than adult hemoglobin ($\text{HbA}$, $\alpha_2\beta_2$) to extract oxygen in the low-oxygen womb.

Homeoviscous Adaptation

The dynamic cellular process of restructuring biological membranes by altering lipid tail saturation levels (e.g., increasing unsaturated fatty acids in cold conditions) to preserve membrane fluidity.

Observed Evolutionary Change

Directly documented microevolutionary shifts, including genomic changes, continuous change in the fossil record, pathogen evolution causing emergent diseases, and the evolution of drug resistance.

Megaplate

A large rectangular petri dish containing spatial concentration gradients of an antibiotic (ranging from zero up to $1{,}000$ times the lethal dose) used to observe bacterial migration, mutation, and the continuous evolution of resistance.

Genome-Wide Heterozygosity

A genetic metric quantifying nucleotide diversity across a genome, which shows a significant decline in populations that have undergone severe bottleneck events.